The present invention relates to cutting tools and, more particularly, to cutting tools using clampable cutting inserts.
In various forms of cutting tools, such as rotating tools and turning tools, it is known to clamp replaceable cutting inserts in pockets on toolholders. Using replaceable, clampable cutting inserts instead of, e.g., cutting inserts that are brazed to a toolholder facilitates replacement of the inserts when worn. Often, the cutting inserts are indexable to a plurality of positions to replace worn portions of a cutting edge of the insert with a sharp portion. A variety of techniques for clamping the replaceable inserts to the toolholder are known, and include pin arrangements, screw or bolt arrangements, and clamping arm arrangements.
Whatever clamping arrangement is used to clamp the insert relative to the toolholder, it is highly desirable that the insert be securely clamped and that any capacity of the insert to move during use is minimized. It is also desirable that the manner of clamping the insert relative to the toolholder be simple to facilitate replacement or indexing of the insert. It is also desirable that the clamping arrangement facilitate precise mounting of the insert relative to the toolholder so that a working cutting edge of the insert will be located in a precise location relative to the toolholder to facilitate automated machining.
Various measures to ensure secure clamping, simple removal or indexing, and precise locating of an insert relative to a toolholder are known. For example, occasionally, the insert supporting surface of the insert will have a slight outward bowing or the insert abutment surface of the pocket of the toolholder will be imperfectly flat so that there is only a single point, line, or area of contact (collectively hereinafter referred to generically as a point of contact) between the two surfaces. Application of high forces to the insert, such as during a machining operation, can cause even a very tightly clamped insert to pivot ever so slightly about that point, line, or area of contact. Such pivoting causes the cutting edge of the insert to move relative to the toolholder and can result in damage to a workpiece or adversely affect the precision to which the workpiece can be machined.
To minimize any tendency of the insert to move relative to a toolholder during use, an insert abutment surface of the insert-receiving pocket of the toolholder might be provided with a recess so that contact between two points of the insert abutment surface and the insert's insert supporting surface can be ensured. By providing a recess in the insert abutment surface or the insert supporting surface, even if an insert supporting surface or an insert abutment surface is less than perfectly flat, there will be two points of contact between the two surfaces, which reduces a tendency of the insert to rock relative to the toolholder.
Typically, inserts have holes for receiving a clamping screw, pin, or clamping arm portion that tends to urge the insert supporting surface(s) against the insert abutment surface(s). It is also known to attempt to minimize a tendency of the insert to move relative to the toolholder by providing a clamping surface on the insert that will contact a clamp surface at least at two points. This is typically accomplished by providing a polygonal clamping surface in the insert for contacting a circular clamping surface of a screw, pin, or arm. U.S. Pat. No. 3,341,921, which is incorporated by reference, discloses such an arrangement. It is desirable to provide a simple arrangement for minimizing any tendency of an insert to pivot relative to a clamping structure.
In accordance with an aspect of the present invention, a cutting insert comprises an insert body having a clamping hole including a clamping surface defining at least part of a non-circular, substantially elliptical cone.
In accordance with another aspect of the present invention, a cutting tool comprises a toolholder comprising at least one insert-receiving pocket, the insert-receiving pocket including at least one side abutment surface, a cutting insert comprising an insert body having at least one insert supporting surface and a clamping hole including a clamping surface defining at least part of a non-circular, substantially elliptical cone, and a clamp having a clamp surface adapted to contact the clamping surface at two contact points such that the at least one side abutment surface and the at least one insert supporting surface are secured in a contacting relationship.